Computer chips, such as microprocessors or microcontrollers, are made of a die and a package. The die has an integrated circuit thereon which may include various circuits such as the microprocessor, memory, power circuits, logic circuit, interface circuits, etc. From the die, signal lines are connected to signal lines of the package. The package has pins or other conductors extending from the package which are used to connect the signal lines of the package to other circuits on a printed circuit board.
In the design of an integrated circuit incorporating a microprocessor, microcontroller, or other logic, it is often difficult to determine the appropriate amount of on-chip memory to incorporate on the die in order to suit the many applications that the integrated circuit may serve. For instance, a large amount of on-chip static memory (i.e., RAM) provides the benefit of fast program execution but has a disadvantage in that the large on-chip RAM requires an initial program loading operation from an off-chip non-volatile memory (i.e., Flash ROM) which has the program content stored therein. The use of such a non-volatile memory may add additional costs to the overall system design which utilizes the integrated circuit, in part because the integrated circuit packages and corresponding pin counts may be quite large. For instance, the interface between the external Flash ROM and the integrated circuit may include a parallel interface having 30 or more pins, which increases the complexity, size, and cost of use of such a system. While the cost and size of such an arrangement may be acceptable in the design of large, complex systems, such as a system that uses multiple chips and large program memories, the cost and size of such an arrangement may be unacceptable if the integrated circuit is to be used in a simple, low-cost system—such as in the design of a smaller microprocessor embedded system.
Alternatively, a large amount of non-volatile memory incorporated on-chip with the integrated circuit has the advantage of relatively low costs when compared with an arrangement that uses on-chip RAM/external Flash ROM. However, such an arrangement has the disadvantage of relatively slower program execution when compared with on-chip RAM/external Flash ROM, which may be unacceptable for use in a large, complex system.
Hence, in order to accommodate the needs of large, complex systems as well as small, low-cost systems, different integrated circuits are designed, manufactured, packaged and sold. As recognized by the present inventor, what is needed is an architecture for an integrated circuit die that may be utilized with large, complex systems using external memory or with small, low-cost systems.
It is against this background that various embodiments of the present invention were developed.